<?php
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$xhtml = array(
	'<{title}>' => 'Classification tree',
	'<{subtitle}>' => 'Written in <span title="Databases 2">CS 3306</span> by <a href="https://y.st./">Alexand(er|ra) Yst</a>, finalised and <a href="https://y.st./en/coursework/CS3306/Classification_tree.xhtml">archived</a> on 2019-05-29',
	'<{copyright year}>' => '2019',
	'takedown' => '2017-11-01',
	'<{body}>' => <<<END
<p>
	We&apos;ve been asked to classify the grades A through F using a classification tree, then identify what grade we would prefer in this class.
	Both of these are odd requests.
	Let&apos;s start with the second.
	What grade would we prefer?
	Who would choose anything besides the highest?
	What kind of question is that!?
	As for the classification tree, you can really group grades however you like.
	There are a lot of sensible answers, and seemingly no definitively correct one.
	We&apos;re not told what to classify grades into, so I chose to classify them into passing grades and failing grades, as well as show which letter grades yield what quantities of grade points.
	It&apos;s also worth noting that grades are a spectrum.
	That means that classification trees are a terrible tool for working with them, as each grade is basically just a range.
	The letters make the grades appear to be categorical values, but they&apos;re actually numeric values.
	We don&apos;t even have multiple ranges to operate on, but only a single range to split up several times.
</p>
<h2>Classification tree</h2>
<img src="/img/CC_BY-SA_4.0/y.st./coursework/CS3306/classification_tree.png" alt="Grade-classification tree" class="framed-centred-image" width="825" height="426"/>
<p>
	To properly classify these grades, we need to know what they mean.
	I mean, sure, we know that the higher up you go in the alphabet, the worse the grade is, and we know that whoever set up the lettered grading system didn&apos;t seem to actually know the alphabet themself, as they skipped the letter E; the possible grades are A, B, C, D, not E, and F.
	F is a failing grade, but aside from that, we can&apos;t group the grades without further context.
</p>
<p>
	To get that context, let&apos;s use this university&apos;s own grading scale.
	It&apos;s worth noting though that at this university, a true passing grade is a 2.0 or above (University of the People, 2016).
	Percents are rounded into letters, then those letters translated back into numbers.
	A C is a 2.0, but a C- is a 1.67 (University of the People, 2019).
	To properly classify grades, we&apos;ll need to look not only at letters, but signs (plus, none, or minus) as well.
	Below, I&apos;ve split the grades up first by letter, then by letter with their sign.
	Finally, at the leaf nodes, we see how many grade points are awarded, and if it&apos;s a passing grade, the node is green.
	If it&apos;s a failing grade, the node is red.
</p>
<p>
	It&apos;s interesting to note a couple quirks in the grading system.
	First, both an A an an A+ result in a 4.0.
	This is how this university grades.
	Second, we expect to see a 0.33 grade, but there is none.
	We skip from 0.0 to 0.67.
	Again, this isn&apos;t a mistake in the tree, but an actual quirk in the university&apos;s grading system.
</p>
<h2>Preferred grade</h2>
<p>
	Obviously, as stated above, I&apos;d prefer a perfect grade.
	That is, I&apos;d like to get 100% on the course.
	I&apos;m not perfect though, and I won&apos;t make that cut.
	None of us are, and I&apos;m doubting any of us will.
	Anything 93% or above would get me a 4.0 though, which would also be very nice.
</p>
<h2>Conclusion</h2>
<p>
	In this case, the classification tree didn&apos;t tell us anything we didn&apos;t already know, because grades are not categorical, but inherently numeric, even though they&apos;re often displayed as opaque letters.
	However, we the research done in order to make the tree did give us some interesting insights.
	First, it&apos;s best to score at least 93% in your courses here at this university.
	If you score at least 93% in every one of your courses, you&apos;ll have a perfect 4.0 $[GPA] when you graduate.
	Secondly, scoring less than 73% in any course is very bad.
	It&apos;s considered a failure.
	Obviously, failure is not what we&apos;re aiming for.
</p>
<div class="APA_references">
	<h2>References:</h2>
	<p>
		University of the People. (2016, August 21). <a href="https://www.uopeople.edu/student-experience/academic-degree-requirements/">Academic Degree Requirements | University of the People</a>. Retrieved from <code>https://www.uopeople.edu/student-experience/academic-degree-requirements/</code>
	</p>
	<p>
		University of the People. (2019, April 9). <a href="https://my.uopeople.edu/mod/page/view.php?id=172943">CS 3306 - AY2019-T4: Syllabus</a>. Retrieved from <code>https://my.uopeople.edu/mod/page/view.php?id=172943</code>
	</p>
</div>
END
);
